全文获取类型
收费全文 | 4003篇 |
免费 | 318篇 |
国内免费 | 175篇 |
专业分类
电工技术 | 304篇 |
综合类 | 151篇 |
化学工业 | 85篇 |
金属工艺 | 240篇 |
机械仪表 | 514篇 |
建筑科学 | 42篇 |
矿业工程 | 46篇 |
能源动力 | 91篇 |
轻工业 | 26篇 |
水利工程 | 14篇 |
石油天然气 | 46篇 |
武器工业 | 43篇 |
无线电 | 830篇 |
一般工业技术 | 251篇 |
冶金工业 | 14篇 |
原子能技术 | 25篇 |
自动化技术 | 1774篇 |
出版年
2024年 | 3篇 |
2023年 | 16篇 |
2022年 | 49篇 |
2021年 | 35篇 |
2020年 | 49篇 |
2019年 | 41篇 |
2018年 | 42篇 |
2017年 | 50篇 |
2016年 | 92篇 |
2015年 | 114篇 |
2014年 | 156篇 |
2013年 | 155篇 |
2012年 | 182篇 |
2011年 | 278篇 |
2010年 | 215篇 |
2009年 | 234篇 |
2008年 | 277篇 |
2007年 | 378篇 |
2006年 | 336篇 |
2005年 | 351篇 |
2004年 | 293篇 |
2003年 | 273篇 |
2002年 | 211篇 |
2001年 | 147篇 |
2000年 | 123篇 |
1999年 | 126篇 |
1998年 | 110篇 |
1997年 | 79篇 |
1996年 | 35篇 |
1995年 | 27篇 |
1994年 | 8篇 |
1993年 | 6篇 |
1991年 | 5篇 |
排序方式: 共有4496条查询结果,搜索用时 0 毫秒
1.
A stochastic model for local disturbances, particularly for a temporal harmonic with random modulations in amplitude and/or phase, is proposed in this paper. Results for the second moment responses of a linear single-degree-of-freedom system to this type of stochastic loading demonstrate a significant change in response characteristics due to a small uncertainty. A local phenomenon may last much longer and resonance may be smeared to a broad range. Integrated with wavelet transform, the proposed approach may be used to model a random process with non-stationary frequency content. Especially, it can be effectively used for Monte Carlo simulation to generate large size of samples that have similar characteristics in time and frequency domains as a pre-selected mother sample has. The technique has a great potential for the case where uncertainty study is warranted but the available samples are limited. 相似文献
2.
基于子波变换的涡街流量传感器信号分析 总被引:6,自引:0,他引:6
长期以来 ,如何提取潜在噪声下的涡街流量信号一直是个问题。流体流速脉动 ,局部阻力 ,随机振动———所有这些因素都给解决这一问题带来难度。文章应用子波变换消噪理论 ,从软件滤波的角度分析了强噪声干扰下的涡街流量信号 ,并提出了单支重构计数方法。分析结果表明 ,这种方法对低流速流量计量效果很好 ,能够有效地扩展量程下限 相似文献
3.
4.
WANGYu-tian LIUZhan-wei HOUPei-guo SHANWei 《半导体光子学与技术》2004,10(3):199-202
The distributed optical fiber sensing technology is overviewed, which is based on Raman scattering light theory. Basic operation principle, structure, system characteristics and signal processing are discussed. This structure and method of the signal processing possess of certain spatial resolution, hence will ensure the practicability of system. 相似文献
5.
Enhancement of islanding-detection of distributed generation systems via wavelet transform-based approaches 总被引:1,自引:1,他引:0
Cheng-Tao Hsieh Jeu-Min Lin Shyh-Jier Huang 《International Journal of Electrical Power & Energy Systems》2008,30(10):575-580
In this paper, a wavelet transform-based approach is proposed to detect the occurrence of islanding events in distributed generation systems. Thanks to time–frequency localization capabilities exhibited by wavelet transform, the approach embedded with this transform technique has grasped the appearance of the islanding event in a highly effective manner. Moreover, for those regions which are in need of a better visualization, the proposed approach would serve as an efficient aid such that the mains power disconnection can be better distinguished. To validate the feasibility of this approach, the method has been validated through several scenarios. Test results supported the effectiveness of the method for the application considered. 相似文献
6.
Ricardo Lima Author Vitae Author Vitae Claudio Reineri Author Vitae Author Vitae 《Computers & Electrical Engineering》2008,34(6):520-530
This paper presents a novel concept for power quality hardware and software architecture. Software tools related to detection, classification and characterization of power quality events can be integrated into a Distribution Control Center in which the interconnection between different subsystems is being carried out through the Internet allowing flexibility to the system. This system is implemented using wavelet analysis applied in all proposed algorithms. Different power quality events are taken as examples to illustrate the capabilities of the proposed method. The obtained results reveal that the proposed architecture is feasible to be implemented as an integral part of a control center system.The proposed system has the property of fast and accurate detection and classification of any power quality disturbance event and introduces a new PQ index determination that allows characterizing any type of disturbance including the non-periodic signals. 相似文献
7.
WAVELET ALGORITHM FOR INTEGRAL OPERATOR EQUATION AND ITS APPLICATIONS TO ELECTROMAGNETIC PROBLEMS 总被引:1,自引:0,他引:1
A brief summary of the basic theory of wavelet is proposed. The properties of wavelet function are discussed. The possible applications of wavelet to electromagnetics are given. Examples show that the wavelet method is feasible and effective for solving electromagnetic problems. 相似文献
8.
地震数据通用压缩文件格式设计 总被引:1,自引:0,他引:1
本文从生产实际需要提出了进行地震数据压缩和制定规范的压缩数据文件格式的要求,按照通用性,兼容性,可扩充性,操作简便,高缩效率几方面的要求设计了通用压缩数据文件格式及一种具体形式,讨论了数据压缩的具体策略和方法,试验表明,采用压缩数据文件格式,不但可以大比例地减小数据存贮空间(压缩比达4:1-10:1),而且可以大大加快数据的I/O速度(提高1倍以上)。 相似文献
9.
用小波变换抑制SAR图像中的斑点噪声 总被引:3,自引:0,他引:3
抑制合成孔径雷达图像中的斑点噪声一直是处理图像并得到准确图像信息的难点,提出了一种基于小波变换抑制合成孔径雷达(SAR)图像中的斑点噪声的方法,对原有的小波变换方法作了改进,能更好地保留图像的边缘信息,并能简化计算量。在仿真实验中使用了合成的模拟图像和真实的合成孔径雷图像,并与以往的小波去噪滤波方法以及一些经典的斑点噪声滤波方法(包括中值滤波,Lee滤波,Frost滤波)进行比较,在综合考虑了滤波算法在均匀区域对斑点噪声的抑制能力以及保留边缘信息能力的情况下,提出的算法有更好的效果。 相似文献
10.
利用小波变换去噪时小波系数方差的估计对去噪结果影响很大。自然图像小波分解后得到的系数在不同的分辨率中差异很大,所以利用邻域估计中心点方差时,不同分辨率应有不同大小的邻域。首先对在邻域中利用极大似然准则估计中心点方差进行分析,再结合自然图像小波分解后的系数在不同分辨率子带中,根据平稳性和重要性选择邻域的大小。最后进行去噪实验,并取得正交小波分解下理想的去噪性能。 相似文献